NCERT Class 11 Biology Biology: Chapter 16 — Excretory Products and their Elimination
This chapter, 'Excretory Products and Their Elimination,' from NCERT Class 11 Biology, details the mechanisms by which animals remove metabolic wastes like ammonia, urea, and uric acid. It explains different excretory strategies such as ammonotelism, ureotelism, and uricotelism, highlighting the conservation of water. The chapter introduces various excretory structures found across the animal kingdom, including protonephridia, nephridia, Malpighian tubules, and antennal glands. It then focuses on the human excretory system, describing the structure of the kidneys, ureters, urinary bladder, and urethra. Key anatomical features like the hilum, renal pelvis, cortex, and medulla are explained, setting the stage for understanding urine formation and regulation.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 11 |
| Subject | Biology |
| Book | Biology |
| Chapter | Chapter 16 — Excretory Products and their Elimination |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 4 minutes |
| Word count | 645 |
Learning outcomes
- Identify major nitrogenous wastes and their toxicity.
- Differentiate between ammonotelism, ureotelism, and uricotelism.
- Describe various excretory structures in invertebrates and vertebrates.
- Explain the anatomy of the human excretory system.
- Understand the basic structure of the kidney, including cortex and medulla.
Vocabulary
| Word | Meaning |
|---|---|
| Ammonotelism | Excretion of ammonia. |
| Ureotelic | Animals that excrete urea. |
| Uricotelic | Animals that excrete uric acid. |
| Protonephridia | Simple tubular excretory structures in Platyhelminthes and some other invertebrates. |
| Nephridia | Tubular excretory structures in annelids. |
| Malpighian tubules | Excretory structures in most insects. |
| Antennal glands | Excretory organs in crustaceans (also called green glands). |
| Hilum | A notch on the inner concave surface of the kidney. |
| Renal pelvis | A funnel-shaped space inside the hilum of the kidney. |
| Calyces | Projections of the renal pelvis into the kidney. |
| Cortex | The outer layer of the kidney. |
| Medulla | The inner layer of the kidney, divided into medullary pyramids. |
The complete chapter text is read in the official NCERT PDF viewer below (streamed from ncert.nic.in). This page provides NCERT Help study material — summary, vocabulary, practice questions, and FAQs — not a full reproduction of the textbook.
Read chapter online
This PDF is loaded from the official NCERT website (ncert.nic.in). Use the page buttons below to read — download is disabled on NCERT Help.
Read page by page below. PDF is streamed from the official NCERT website — no download button on this page.
Practice questions
- What are the three major forms of nitrogenous wastes excreted by animals? Answer: Ammonia, urea, and uric acid.
- Which type of animal excretes ammonia and why is it toxic? Answer: Ammonotelic animals (e.g., bony fishes, aquatic amphibians) excrete ammonia. It is the most toxic form and requires a large amount of water for elimination.
- Name the excretory structures found in earthworms and insects. Answer: Earthworms have nephridia, and insects have Malpighian tubules.
- Where are the kidneys located in the human body? Answer: Kidneys are located between the last thoracic and third lumbar vertebra, close to the dorsal inner wall of the abdominal cavity.
- What is the hilum of the kidney? Answer: The hilum is a notch on the inner concave surface of the kidney where the ureter, blood vessels, and nerves enter.
Frequently asked questions
What is the main function of the excretory system?
The excretory system removes metabolic wastes and excess substances from the body to maintain homeostasis and conserve water.
Why do mammals excrete urea instead of ammonia?
Mammals excrete urea because it is less toxic than ammonia and requires less water for elimination, aiding in water conservation.
What are Malpighian tubules?
Malpighian tubules are the primary excretory organs in most insects, responsible for removing nitrogenous wastes and osmoregulation.
Describe the location and appearance of human kidneys.
Human kidneys are reddish-brown, bean-shaped organs located in the abdominal cavity, between the last thoracic and third lumbar vertebrae.
What is the difference between the renal cortex and medulla?
The renal cortex is the outer layer of the kidney, while the renal medulla is the inner layer, containing medullary pyramids.
Which animals are called ureotelic?
Mammals, many terrestrial amphibians, and marine fishes are called ureotelic because they mainly excrete urea.
Related resources
Important topics
Topics covered
NCERT Class 11 Biology — Biology — Chapter 16 — Excretory Products and their Elimination. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.